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<head><meta charset="utf-8"><title>Issue #34426 help · wg-traits · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/index.html">wg-traits</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/Issue.20.2334426.20help.html">Issue #34426 help</a></h3>

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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/Issue%20%2334426%20help/near/160959896" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Osspial <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/Issue.20.2334426.20help.html#160959896">(Mar 16 2019 at 17:28)</a>:</h4>
<p>Hi! I'm trying to look into why <a href="https://github.com/rust-lang/rust/issues/34426" target="_blank" title="https://github.com/rust-lang/rust/issues/34426">#34426</a> is happening since it's an issue that's preventing my code from compiling, and I <em>think</em> I've found what's causing the problem, but I'm not entirely sure what the proper solution for it is.</p>
<p>looking at <a href="https://github.com/rust-lang/rust/blob/master/src/librustc_typeck/check/dropck.rs#L143-L237" target="_blank" title="https://github.com/rust-lang/rust/blob/master/src/librustc_typeck/check/dropck.rs#L143-L237">https://github.com/rust-lang/rust/blob/master/src/librustc_typeck/check/dropck.rs#L143-L237</a>, it seems that for HRTB clauses, the RegionKind::ReLateBound in the HRTB's Predicate::Trait variant isn't getting properly normalized, leading to the issue. My first guess for solving this would be to try and use the same trait-bound checking mechanisms used elsewhere in the codebase (which seems to be the traits::fulfill machinery), but I think the comment at 198 says that that doesn't work.</p>
<p>However, I don't understand what exactly that comment is saying. What exactly are outlives predicates and region inference constraints, and why is it bad to turn the first into the second?</p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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